Duggap is right, and so is HutSiteDigger. Here's a scan of the 1879 US Patent's diagram of the horse-harness "buckle shield" (strap-buckle cover), with date and inventor's name. Having a decorative emblem or a cut-out design on it doesn't matter -- it's the object's basic form that matters.
I'll also include a photo showing one just like Finderfarthing's, showing the exact same patent date (Dec. 16, 1879), in full.
Note: For double-magnification If you can't read it, click on the photo once, then when the next version of it appears, click on that one.